4:21 PM Abstract No. 190 Quantitative 4D digital subtraction angiography: a novel technique for quantifying changes in hepatic arterial flow during transarterial embolization

Degree of stasis affects response to and survival after transarterial embolization (TAE). Despite this, angiographic endpoints during TAE are subjective and highly variable. Time-resolved 3D-Digital Subtraction Angiography (4D-DSA) is a recently developed technique that permits quantification of blood flow and velocity. We aimed to validate the accuracy of 4D-DSA for quantifying hepatic arterial blood flow/velocity along with its ability to show changes in flow during TAE. Hepatic arteriography and TAE of two of the four liver lobes were performed in five female domestic swine using 100-300μm and 300-500μm Embosphere Microspheres. Conventional 2D- and 4D-DSAs were performed before, during, and after each embolization. From the 4D-DSA reconstructions, blood flow and velocity values were calculated for the common, right, left and lobar hepatic arteries using a pulsatility based algorithm. 4D-DSA flow and velocity values were compared to those measured using an intravascular Doppler wire with a linear regression analysis. Paired t-tests were used to compare data before and after embolization. There was a statistically significant but suboptimal correlation between the two methods (r = 0.36, N = 42, p>.05). The Doppler measurements were positively biased in vessels with high pulsatility (χ2(1, N = 11) = 13.3, m = .55, b = 4.5, p>.05). This might be related to the difference in data acquisition (average peak in Doppler vs spatially averaged velocity in 4D-DSA) or the flow dynamics of blood and contrast. 4D-DSA performed mid-embolization showed a global reduction in hepatic blood flow and velocity in the embolized liver when compared to preembolization (4.5 ± 0.7 vs 10.9 ± 1.9 cm/s, p = 0.008). Complete stasis was achieved in all cases, at which point reliable measurements could not be made using 4D-DSA due to low signal. 4D-DSA can accurately reflect changes in hepatic arterial blood flow during TAE and it is a promising method for quantifying blood flow and velocity during angiography. While further work is needed to optimize the injection protocol and acquisition parameters, 4D-DSA may provide an objective, C-arm based means of determining angiographic endpoints during embolization.